Mastic is excreted by the resin glands of certain trees and dries into pieces of brittle, translucent resin. When chewed, the resin softens and becomes a bright white and opaque gum. The flavor is bitter at first, but after some chewing, it releases a refreshing flavor similar to pine and ceda
 
Mastic (Pistacia lentiscus) is an evergreen shrub found throughout the Mediterranean. The sap (resin) from its trunk is used to make medicine.
Mastic might help reduce stomach acid and protect the lining of the stomach and intestine. It might also have antibacterial effects and reduce swelling.
People use mastic for stomach ulcers, indigestion, Crohn disease, wound healing, and many other conditions
Don't confuse mastic with gum arabic. These are not the same